The present invention generally relates to a method for selectively obtaining antioxidant rich aqueous extracts from citrus fruits. More specifically, the present invention relates to a method for obtaining a balanced enriched composition of simple phenols, polyphenols, bioflavonoids, flavones and flavonones, to control oxidation processes, from citrus aqueous extracts obtained from cells, core, membrane, frit and peels of citrus fruits.
Citrus fruits are a growing industry with significant world importance. Citrus fruits (such as lime, lemons, tangerins, oranges and grapefruits) are utilized primarily for juice recovery.
The by-products industry has also a potential for growth since products like terpaneless oils, pectins, alcohol, wine, natural flavors and aromas, and vinegar have also been produced from citrus fruit residues. The peel residue is the primary by-product, amounting to up to 30% of the fruit mass. Cells, core, membrane and frit residues present additional 20% of by-products. In most cases, this huge amount of waste material is the source for cattle feed only, while in other cases products such as molasses, cold-pressed oils, d-limonene, pectin and flavanoids can be extracted and used. Another method for utilization of the by-products stream, practiced in the last decade by few companies, is concentrating the aqueous extract to obtain higher solid extract which may be sold as such, or upgrading the solid extracts, to improve the organoleptic properties by removal of the so called xe2x80x9cundesirable compoundsxe2x80x9d on resin columns.
The protection that fruits and vegetables provide against diseases, including cancer and cardio- and cerebrovascular diseases, has been attributed to the various antioxidants, especially antioxidant vitamins or provitamins, including ascorbic acid and tocopherols. However, the majority of the antioxidative activity of a fruit or a vegetable may be from compounds other than vitamin C, vitamin E, or xcex2-carotene. It was recently demonstrated (Pratt, D. F. and Hudson, B. J. F., xe2x80x9cNatural Antioxidants in Foodsxe2x80x9d, Elsevier Applied Science, London (1990), p.171-198) that flavanoids, found in human diets, have also antioxidative activity.
In certain fruits some flavanoids have much stronger antioxidant activities against peroxide radicals than vitamins (vitamin E, vitamin C, glutatione).
Phenolics, in the present invention, are defined as substances possessing an aromatic ring, leaving one or more hydroxyl substituents including their functional derivatives.
The most ubiquitous phenols are polymeric and water-insoluble liquids that are found in vascular plants. However, many of the food phenolics are soluble in water. Phenolics found in feeds generally belong to a subclasses known as phenolic acids, flavonoids, lignans, stilbenes, coumarins and taunins.
When the phenolic skeleton is attached to a sugar glycoside moieties, through an OH group, the materials will be called xe2x80x9cglycosyl-flavanoidsxe2x80x9d or, in short, xe2x80x9cflavonoidsxe2x80x9d. The xe2x80x9cglycosyl-flavanoidsxe2x80x9d are more water soluble and have a more complex structure than the phenolic skeleton materials.
In all phenolic compounds in general, and in most flavanoids and flavonoids, there can be found functional phenolic groups capable of quenching radicals or serving as transition metal scavengers. Also, it seems that certain combinations of phenolics exhibit better activities (synergism) than others.
Flavanones and flavanonols are found mainly in citrus fruits. Some citrus flavanones are naringenin, eriodictyol, hesperidin and isosakuranetin. Some of the most common citrus flavanone-glycosides are natrirutin, naringin, hesperedin and neohesperidin.
Citrus fruits consist mainly of 3-deoxy flavanols (differing from flavanols in position 3, flavanols have an hydroxy group) that are termed flavones. Some common flavones are tangeretin, nobitetin and sinensetin.
Simple phenols, (such as cinarnic and limoneic acid), polyphenols and glycosyl-flavanoids are found mainly in the aqueous fraction of the orange, while the flavanones and flavanonols are less water soluble and expected to reside in the xe2x80x9cpeel oilsxe2x80x9d. (naringin is water soluble whereas naringenin is more xe2x80x9coil solublexe2x80x9d).
Today""s world is very aware of the health benefits offered by citrus fruits in terms of vitamins and other additives, and the consumption of citrus juice and drinks is increasing dramatically every year.
Naringin (in grapefruits) and hesperidin (in oranges) are the two major flavanoid-glycosides present in the citrus fruits, and are primarily concentrated in the peel and the tissue of the fruit. Attempts were made to extract and purify both flavanoids (Braddock, R. J., By-products of citrus fruit, Food Technology, 9,1995 p.74-77), but the anti oxidation capacity of orange, grapefruit, or any other specific citrus extracts, was not explored. Furthermore, no data is available regarding fractionation and enrichment of the possible active matter (bioflavonoides and/or simple and polyphenols) in each of the fruit fractions (cells, core, frit and peels). The existing debittering technology relates to recovery of bioflavenoids only (mainly naringin and hesperidin), by method of alkaline water extraction utilizing caustic solutions for pH control.
The present existing technologies are based on absorption/adsorption and resin extraction, and the removal/recovery of the products are not selectively done. Moreover, the alkaline conditions could change chemical structures, mainly by hydrolyzing the ester bonds between the sugars and the flavonoids and partially oxidizing the phenolic groups. In addition, the existing technology encounters environmental hazards.
Various attempts were made to obtain antioxidant materials from fruits. DE patent No. 2525590 teaches a process for obtaining, via solvent extraction of oil a non-specific segment, which contain (among other compounds) some bioflavonoids. However, DE patent No. 2525590 relates only to the oily phase of the citrus fruit and not to the aqueous (juice) fraction. EP patent No. 657169 describes a method for obtaining a fruit polyphenol from unripe fruits of Rosaceae by subjecting the unripe fruits of Rosaceae to pressing and/or extraction and then purifying the resulting juice or extract. However the invention relates only to the unripe fruits of Rosaceae and not to citrus fruits. Hence, the polyphenols obtained are of different structures and properties.
Up to this date no direct correlation between each of the above phenolic compounds in citrus fruits to their xe2x80x9cantioxidant activityxe2x80x9d was shown.
In the present invention it is shown, for the first time, that the composition of certain polyphenols, simple phenols and/or flavones and/or flavanoids derived from citrus fruit, can offer, in themselves and combined with each other, antioxidant capacities that are more attractive than many known synthetic or natural antioxidants from common vegetables or fruits.
As opposed to the work done up to this date, the present invention relates to an environment friendly method for selectively extracting unique and well-balanced synergistic compositions of phenolics (combinations of simple phenols, polyphenols and flavonoids) from citrus fruits, that exhibit strong antioxidant capacities, superior to the isolated flavanoids such as naringin or herperidin.
The method of the present invention also differs from the work done up to date in that, otherwise discarded compounds (xe2x80x9cundesirable compoundsxe2x80x9d), are eluted from the resin, allowing for the possibility, during the elution process, to selectively enrich each of the fractions by its active matter. This additional elution step gives a significant advantage over the alkaline or acidic xe2x80x9cwater extracted fractionsxe2x80x9d of the methods used today, being xe2x80x9cblindxe2x80x9d to their internal product distribution and activity.
The present technology offers the additional advantage of selectivity of extraction/recovery by utilizing advanced citrus down stream engineering based on chromatographic selective separation that was not applied for the purpose of obtaining a selective, rich in antioxidants, extract from citrus fruits, in any of the present/known technologies.
The present invention relates to a method for selectively obtaining antioxidant rich aqueous extracts from the cells, frit, core, and peels of citrus fruits, comprising;
employing water treatment and solids extraction of the citrus fruit;
employing separation technology and/or membrane technology on the said extracts, resulting in a serum;
submitting said serum to an adsorption process on resin, preferably in columns preconditioned by passing deionized water through the column, and charging the columns with solvents, preferably an edible solvents such as ethanol, isopropanol or ethyl acetate, wherein the solvent to resin volume ratio is between 1:1 to 10:1; and
eluting the adsorbed antioxidant compounds from the resin by solvents, preferably edible solvents such as ethanol or ethyl acetate, and collecting the solvent. For selectivity purposes the solvent may be collected fraction-wise.
The resin column may be further charged with other blends or combinations of solvents and another selective fraction or fractions may be further collected.
The collected solvent fractions may be further evaporated to obtain dry phenolic compounds.
In the method of the present invention antioxidant rich extracts are obtained selectively. This selectivity is achieved by collecting the fractions according to charged solvent sequence or polarity of charged solvent or the flow rate of the charged solvent or the hydrophobic hydrophilic attraction to the resin.
The present invention further relates to selectively obtained antioxidant rich extracts from citrus fruits obtained by said method, and compositions containing them. These compositions contain specific simple phenols, polyphenols, flavones and flavonones and bioflavanoids such as naringenin, eriodictyol, hesperedin, isosakuranetin, and the corresponding bioflavonoids such as narirutin, naringin, hesperedin, neohesperidin, tangeretin, nobiletin and sinensetin, or blends of simple phenols such as limonin, nomelin, cinamic acid as well as polyphenols and Vitamin C, or mixtures thereof which work in synergism to provide superior health benefits.
Preferably, in the compositions of the present invention, the total polyphenols and phenols exceeds 30%, and the ratio of total polyphenols and phenols to bio-flavonoids is from approximately 1:3 to approximately 3:1.
The present invention is illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein the elements having the same reference numeral designations represent like elements throughout and wherein:
FIGS. 1(A) and 1(B) are graphs presenting copper-ion-induced LDL oxidation as a function of antioxidant concentration to show anti-oxidative capacity of RSPP, RSBF and Hesperidin;
FIG. 2 is a graph presenting LDL oxidation as a function of time for RSPP, RSBF and Naringin;
FIG. 3 is a graph presenting LDL oxidation as a function of time for RSPP and Hesperidin;
FIGS. 4(A) and 4(B) are graphs presenting AAPH-induced LDL oxidation as a function of antioxidant concentration to show anti-oxidant capacity of RSPP, RSBF and Hesperidin;
FIGS. 5(A) and 5(B) are graphs presenting AAPH-induced LDL oxidation as a function of antioxidannt concentration to show anti-oxidative capacity of RSPP, RSBF and Naringin; and
FIG. 6 is a graph showing radical scavenging capacity, as function of time, of RSPP, RSBF and Hesperidin.
The present invention relates to a method for selectively obtaining antioxidant rich extracts from citrus fruits. In general, the said method comprises the following steps:
(1) Extensive water treatment and solid extraction (water, acidic or neutral, co-current or counter-current), followed by (2) utilization of separation technology (presses and/or finishers and/or decanters and/or other filter centrifugesxe2x80x94any of the above or combinations thereof) and/or membrane technology (microfiltration, ultrafiltration and nanofiltrationxe2x80x94any of the above or combination), resulting in serum, followed by (3) an adsorption process (by physical or chemical hydrophilic/hydrophobic interaction), carried out on columns packed with carefully selected edible polymeric adsorbent (or by direct contact with the adsorbent other than on columns). (4) Regeneration of the adsorbed matter which builds up on the resin columns (or the adsorbent). The active matter in the present invention is known also in the citrus industry as xe2x80x9cundesirable compoundsxe2x80x9d but is, in fact, high potent active materials. The adsorbed matter is extracted (removed) from the columns by edible solvents to obtain a blend enriched in phenolic compounds (also referred to as RSPP-rich specific phenols and/or RSBF-rich specific bioflavonoids). The blends include balanced compositions of phenolic acids, polyphenols and bioflavonoids.
The method of the present invention allows for control over the internal product composition balance between simple and polyphenol flavanoids and flavonoids. This control is achieved by collecting the fractions according to hydrophobi hydrophilic attraction to the resin and the polarity of the solvent.
In the method of the present invention, the existing practice of resin treatment (which is characterized by extensive washing of columns with caustic soda and corrosive acids resulting in severe effluent problems and significant reduction of the absorption capacity of the resin), is replaced by passing either edible or non edible solvents (edible solvents such as alcohols, aldehyds, ketons, acids, esters, or any combination thereof, and the non edible solvents such as DMSO, DMA, DMF and dioxane or any combination thereof) through the columns, collection of fractions of the column effluent and optionally evaporation of the solvent from the collected fractions to obtain dry RSPP mixtures and recycled solvent available for the next treatment. The ratio of solvent to resin volume may vary from 1:1 to 10:1 and the solvent is charged to the top of the column drop-wise at a rate of 0.5 to 4.0 BV (bed volume) per hour. The RSPP fractions differ according to their hydrophobic/hydrophilic attraction to the resin and the polarity of the solvent.
The RSPP blend, extracted by the method of the present invention (termed rich specific phenols and includes non-glycosides, simple phenols and polyphenols which are esterified; non-bioflavanoid compounds), has maximum antioxidative capacity exhibited on copper-ion-induced LDL oxidation (FIG. 1).
The method of the present invention allows for selective extraction of fractions rich in polyphenols, more than fractions in which the flavonoids are in lower concentration and markedly more than pure hesperidin or naringin (FIGS. 2,3xe2x80x94as a function of time). The selective extraction products have antioxidant capacity to induce also the AAPH-LDL oxidation markedly more than pure hesperidin or naringin and more than commercial blends of citrus bioflavonoids.(FIGS. 4,5 and table 1). This advantage is maintained also for combined antioxidant systems where the RSPP is blended with Vitamin C and compared to commercially available products (table 1).
Similar trends have been detected by an additional method describing the radical scavenging capacity of the active extract as a function of time, as is shown in FIG. 6 (vs the hesperidin).
The advantages of the method of the present invention are that this method:
permits good control over the internal product composition so that the extracted matter will be rich in polyphenols or rich in flavonoids, according to the antioxidation requirements.
achieves antioxidation capacity of the active matter which is superior to pure hesperidin and/or naringin.
permits to extract active matter to act primarily as Cu++ scavenger or peroxide radical quencher. The fraction, rich in polyphenols, will act as a metal scavenger.
achieves antioxidant activities against peroxide radical (ORACROO activity) that are better than many other vegetable extracts and that are controlled by the extraction process.
regenerates resin columns without utilization of strong bases or acids.
The said invention will be further illustrated by the following examples. These examples do not intend to limit the scope of the invention but to demonstrate and clarify it only.